Dental laser

ABSTRACT

An apparatus for removing dental enamel and dentin. This apparatus is also capable of cutting soft tissue. The apparatus includes a laser which, when activated, produces a laser pulse having a wavelength of between 1.5 and 3.5 microns, a beam diameter at the target site in the range of 10 to 5,000 microns, a pulse duration of between several picoseconds and several milliseconds, an energy level of between 0.1 millijoules and five joules per pulse, and pulse repetition rates from one pulse per second to 10,000 pulses per second. The pulse is focused on the dental enamel or dentin thereby reaching high enough energy densities to vaporize the material. In the case of soft tissues, a special tip is used to concentrate the laser on the tissue so that cutting action can be easily executed.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of copending application(s) Ser. No. 07/343,399filed on Apr. 25, 1989, now U.S. Pat. No. 5,257,935, which applicationis a continuation-in-part of U.S. patent application Ser. No. 167,739,entitled DENTAL LASER, filed on Mar. 14, 1988, now abandoned.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates generally to lasers and, moreparticularly, to a dental laser which is particularly suited forremoving dental enamel and dentin, and for cutting soft tissues.

II. Description of the Prior Art

Diseased dental enamel and diseased dentin have traditionally beenremoved by the dentist by a mechanical drill On the other hand, diseasedsoft tissue in the mouth is traditionally removed by cutting with ascalpel, scissors and the like. Both of these methods are uncomfortablypainful to the patient, and the results produced have certain drawbacks.

There have, however, been a number of previously known experiments inwhich teeth have been subjected to laser radiation to determine thealteration, if any, of the physical or chemical properties of the dentalenamel. These tests have shown that the hydroxyapatite crystals, thatform the enamel, fuse somewhat at the surface when lased and render theenamel more impervious to acids of a type which cause tooth decay.

These previous studies have, however, also concluded that the lasercannot be used to remove tooth decay since the power level necessary forthe laser to form an opening in the enamel also significantly heats thetooth and can damage the dental pulp and kill the tooth nerve. For thisreason, dental lasers have not been previously used to remove toothdecay or dentin. The lasers that were used previously were operated indifferent modalities and used different laser materials and were ofdifferent wavelengths than those proposed herewith.

In prior U.S. Pat. No. 4,521,194, a method for removing incipientcarious lesions from the teeth is disclosed. Such lesions areessentially a surface defect formed on the tooth so that their removaldoes not require forming an opening in the dental enamel. Furthermore,in that application it was believed that a laser should not be used toform an opening in the dental enamel and dentin for the above-discussedreasons.

U.S. Pat. No. 4,818,230 discloses a method for removing decay that hasinvaded the dentin as well as removing soft gum tissue in which the peakpulse energy reaches 100 millijoules. In some applications, however, ahigh energy per pulse is desireable, even if some cooling of the toothand/or tissues is necessary.

SUMMARY OF THE PRESENT INVENTION

The present invention provides an apparatus for dental procedures in themouth.

In brief, the present invention comprises a laser and means foractivating the laser so that the laser produces a pulsed output having abeam diameter in the range of 10-5000 microns, a pulse duration in therange of several picoseconds to several milliseconds, an energy level ofbetween 0.1 millijoules and five joules per pulse (preferably in therange of 100 millijoules to five joules), and pulse repetition rate offrom 1 to 10,000 pulses per second.

In another configuration, a small tip is used to concentrate theradiation so that effective soft tissue cutting can be made. The laseralso produces an output pulse having a wavelength in the range of1.5-3.5 microns These wavelengths have been shown to be particularlyeffective for removing dental enamel and dentin. It has also been shownthat these wavelengths are highly absorbed by soft tissue in the mouth.The exposures to enamel can be made without significantly heating thetooth or damaging the pulp and the tooth nerve. Furthermore, it has beenfound that a laser utilizing this wavelength together with theabove-mentioned characteristics or laser parameters is capable ofeffectively and efficiently forming an opening in dental enamel ratherthan fusing the enamel as taught by the previous studies. Similarly,when used with soft tissues, the laser simultaneously sterilizes thetreatment area.

In one form of the invention, the laser is preferably an Erbium dopedytterium-aluminum-garnet (YAG) laser having a wavelength ofsubstantially 2.94 microns. In the second embodiment of the invention,the laser is preferably a Holmium doped crystal laser, having awavelength of substantially 2.06 microns. Other types of pulsed laserscan, however, alternatively be used.

In use, the laser is repeatedly pulsed until the decay, enamel, dentinor tissue is eradicated. Furthermore, in practice, it has been foundthat the apparatus of the present invention removes decay, enamel anddentin painlessly and simultaneously sterilizes.

BRIEF DESCRIPTION OF THE DRAWING

A better understanding of the present invention will be had uponreference to the following detailed description when read in conjunctionwith the accompanying drawing, wherein like reference characters referto like parts throughout the several views, and in which:

FIG. 1 is a perspective of a preferred view of a preferred embodiment ofthe present invention;

FIGS. 2 and 3 are diagrammatic views illustrating the operation of thepreferred embodiment of the present invention;

FIG. 4 is a cross-sectional view taken substantially along line 4--4 inFIG. 3;

FIG. 5 is a view similar to FIG. 4 but showing a different type ofdecay; and

FIG. 6 is a partial side view showing a modification of the presentinvention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

With reference first to FIG. 1, a preferred embodiment of the apparatusof the present invention is thereshown and comprises a laser 10 which,upon activation, generates a laser beam 12. A conventional means 11 isemployed to energize or activate the laser 10. The laser beam 12 isfocussed into a fiber by a lens 13.

The laser 10 produces a pulse output having a beam with a pulse durationin the range of several picoseconds to several milliseconds and anenergy of 0.1 millijoules per pulse to five joules per pulse, and pulserepetition rates of from 1 to 10,000 pulses per second. In addition, thelaser 10 has a wavelength of between 1.5 and 3.5 microns which has beenshown to be particularly effective in eradicating dental enamel anddentin. The laser beam diameter at the target is between 10-5000microns. It has also been shown that these wavelengths are veryeffective in cutting soft tissues.

Although any type of laser can be employed, in one form of theinvention, the laser is an Erbium doped ytterium-aluminum-garnet (YAG)laser having a wavelength of substantially 2.94 microns. Alternatively,the laser 10 is a Holmium crystal laser having a wavelength of 2.06microns. In both cases, these wavelengths have proven to be particularlyeffective for enamel interaction and thus for the eradication of enamel.Enamel 15, of course, is much harder than dentin so that the laserswhich eradicate the enamel also are effective in eradicating dentin anddecay.

With reference now to FIG. 1, 2 and 4, the laser 10 is employed toremove tooth decay 14 in the tooth 18, which, as shown in FIG. 4, hasinvaded the tooth dentin 19. A laser output beam 12 is aimed at decay 14through any conventional delivery system 20, such as an optical fiber21. A lens 13 is used to focus the output from the laser 10 into one endof the fiber 21 while the other end of the fiber 21 is focussed on thetarget, i.e. enamel 15, dentin 19, decay and/or soft tissue. A singleoptical fiber, furthermore, has proven particularly effective for use indental applications since it may be bent easily to direct or deliver thelaser beam to the desired location within the small area of the humanmouth.

Other aiming systems can, of course, alternatively be used. For example,as best shown in FIG. 6, a contacting tip 25 may be employed with theoptical fiber 21. The tip 25 is typically conical or frustoconical inshape and concentrates the laser energy at its apex 27. The apex 27 thencontacts the target 29 (enamel, dentin, decay or soft tissue) inoperation. Furthermore, the tip 25 has proven particularly effective forremoving soft tissue.

With reference now to FIGS. 2-4, upon activation of the laser 10 by themeans 11, the laser eradicates by vaporization the tooth decay 14 and/orenamel and/or dentin 19 in the area 22 of the laser beam impingement toa depth 26 (FIG. 4) into the decay 14 in the dentin 19. Thereafter, thelaser is reaimed through the delivery system 20 to the remainingportions of the tooth decay 14 and reactivated until the entire decay 14is eradicated or obliterated from the tooth.

The energy level of the laser is preferably adjustable to produce energypower levels of between 0.1 millijoules and 5 joules whichcorrespondingly varies the depth 26 of the decay 14 obliterated by thelaser 10, or the amount of enamel or dentin that is removed. Forinteracting with tooth decay, which has invaded a tooth to only arelatively shallow depth, relatively low laser energy is used. On theother hand, to remove enamel and dentin, then high energy levels need tobe used. It is for this reason that a wide range of energy levels needto be available.

The precise phenomenon which occurs when the tooth is lased and thedecay obliterated is not precisely understood due primarily to theextremely short time period involved during the lasing operation. It hasbeen found, however, that both the dental enamel and the dentin isobliterated without significantly heating the tooth and thus withoutdamaging the nerve. Conventional means, such as a water spray, followedby an air jet to blow away most of the water and dry the field, can beused if heating does occur.

With reference now to FIG. 5, in some situations the decay 14 is insidethe tooth 18 and is surrounded by healthy dentin 19 and healthy enamel15. In this case, it is necessary to remove both the healthy enamel 15and healthy dentin 19 before the decay can be removed by the laser. Thishas previously been done by drilling.

As best shown in FIG. 2, the laser of the present invention alsoeffectively removes disease 30 from soft tissue 32, such as gum tissue.In order to remove soft tissue, a special tip may be used. The laseruses low energy levels, but high repetition rates of the same wavelengthas previously described, and the tip is placed at the diseased portionof the soft tissue and a cutting action is initiated by the means 11.Once activated, the disease portion 30 of the soft tissue 32 is cutaway, thus removing the disease and, simultaneously, sterilizing thesoft tissue. Repeated activations of the laser may be required tocompletely eradicate the diseased portion 30 of the soft tissue and theremoval of the diseased portion 30 is painlessly accomplished.

In some soft tissue procedures, relatively high energy pulse powers aredesirable. Such procedures would include endontic procedures such asroot canals, apicoectomies, pulpectomies as well as other soft tissueprocedures such as curetage and flap surgery. These higher powers aredesirable since they simultaneously remove the diseased tissue andsterilize the treatment area. Cauterization of the work area is alsoachieved with these higher powers which minimizes bleeding together withthe health risks associated with bleeding.

Having described our invention, many modifications thereto will becomeapparent to those skilled in the art to which it pertains withoutdeviation from the spirit of the invention as defined by the scope ofthe appended claims.

We claim:
 1. Apparatus for removing dental enamel, dentin and/or softtissue, sterilization in a mouth and/or for endodontic applications at atarget site comprising:a laser, means for activating said laser so thatsaid laser produces a pulsed output having a wavelength of between 1.5and 3.5 microns, a beam diameter at the target site in the range of10-5000 microns, and an energy of 0.1 millijoules to five joules, meansfor delivering said pulse to dental enamel, dentin and/or soft tissueand/or sterilization site and/or endodontic treatment area to therebyeradicate the dental enamel, dentin and/or soft tissue and/orsterilization and/or perform endodontic procedures.
 2. The invention asdefined in claim 1 wherein the laser has a pulse repetition rate of 1 to10,000 pulses per second.
 3. The invention as defined in claim 1 whereinsaid laser is a yttrium-aluminum-garnet (YAG) laser.
 4. The invention asdefined in claim 1 wherein said laser is a Holmium doped laser.
 5. Theinvention as defined in claim 4 wherein said laser has a wavelength ofsubstantially 2.06 microns.
 6. The invention as defined in claim 4wherein said laser is a glass laser.
 7. The invention as defined inclaim 4 wherein said laser is a crystal laser.
 8. The invention asdefined in claim 1 wherein said laser is an Erbium doped laser.
 9. Theinvention as defined in claim 8 wherein said laser has a wavelength ofsubstantially 2.94 microns.
 10. The invention as defined in claim 8wherein said laser is a glass laser.
 11. The invention as defined inclaim 8 wherein said laser is a crystal laser.
 12. The invention asdefined in claim 1 wherein said delivering means comprises means forfocussing said pulse on one end of an optical fiber strand.
 13. Theinvention as defined in claim 12 and comprising a contact tip adjacentthe other end of said strand.
 14. The invention as defined in claim 13Wherein said tip is conical in shape.
 15. The invention as defined inclaim 12 wherein at least a portion of said optical fiber strand isflexible.